DNase I is an endonuclease found in mammals and other eukaryotes that cleaves phosphodiester linkages in DNA. It acts on single-stranded DNA, double-stranded DNA, and chromatin to reduce the size of DNA strands and yield 5′-phosphate-terminated polynucleotides with a free hydroxyl group. Human DNase I and certain variants are disclosed in U.S. Pat. Nos. 5,279,823; 6,348,343; and 6,391,607.
DNase I has been used to treat cystic fibrosis. Cystic fibrosis is a disease caused by mutations in a specific cellular chloride channel regulator, the cystic fibrosis transmembrane conductance regulator protein (CFTR). It is the most common autosomal recessive disease in Caucasians. The mutations prevent normal passage of Cl− ions through the chloride channel lumen of the airway epithelial cell membranes, resulting in a relative impermeability to chloride ions in the epithelial cells of the lungs and a depleted airway surface liquid volume. As a result of impaired function of the CFTR protein, mucus viscosity is increased and the thickened, tenacious secretions block the airways in the lungs of cystic fibrosis patients. The large amounts of viscous mucus blocking the airways in the lungs of cystic fibrosis patients causes a propensity for chronic infection, resulting in inflammation, progressive airway and parenchymal damage, bronchiectasis, pulmonary exacerbations, lung function decline and frequently premature death. Even though improved treatment has increased survival, the median predicted lifespan is only 35 years and patients experience significant morbidity and hospitalizations. Approximately 95% of cystic fibrosis deaths are due to lung infection.
In 1993, the U.S. Food and Drug Administration (FDA) approved a formulation of recombinant human DNase I for the treatment of cystic fibrosis. It was the first treatment approved by the FDA for cystic fibrosis in 30 years. The approved product is marketed in the U.S. by Genentech, Inc. under the brand name PULMOZYME®. PULMOZYME® is believed to act by cleaving DNA in the thick mucus secretions that are a hallmark of cystic fibrosis. This tends to liquefy the mucus, making it easier for the body to clear the mucus from the airways, with consequent improvement in airway function and lessened susceptibility to bacterial infections.
The success of PULMOZYME® in treating cystic fibrosis prompted its study in bronchiectasis, another lung disease where mucus buildup was thought to play a role. Unfortunately, a large clinical trial of bronchiectasis patients not only failed to demonstrate any benefit from PULMOZYME®, but suggested that such treatment was potentially harmful (O'Donnell, et al., 1998, Chest 113:1329-1334).
Sarcoidosis is a disease involving granulomas (abnormal collections of inflammatory cells), often present as nodules, which can form in various organs, including the skin, heart, liver, lungs, nervous system, and gastrointestinal tract. The granulomas are characterized by the accumulation of neutrophils, monocytes, macrophages, and activated T cells, as well as the production of elevated levels of inflammatory mediators such as tumor necrosis factor-α (TNF-α) interferon-γ, and interleukin-2.
The cause of sarcoidosis is unknown, but there is speculation that it is triggered by an immune reaction to some infectious or environmental antigen that continues after exposure to the antigen ceases. The lung is the most commonly involved organ in over 90% of cases. Most patients do not exhibit symptoms and are unaware that they have sarcoidosis. Half of all asymptomatic sarcoidosis patients are diagnosed after routine chest x-ray. The most common presenting symptoms are cough and dyspnea. The most common diagnostic clinical signs are: i) dyspnea, ii) cough, iii) skin rash, iv) inflammation of the eyes, v) weight loss, vi) fatigue, vii) fever, and viii) night sweats. Due to the non-specific nature of granulomas, sarcoidosis is generally diagnosed by excluding other diseases such as malignancies and infections. The lung in sarcoidosis typically displays the characteristic bilateral hilar lymphadenopathy on chest x-ray. Reversible stages of sarcoidosis (Scadding Radiographic Stages I and II), characterized by nodular reticular infiltrates and “ground-glass” appearance of lung parenchyma on chest x-ray, may not require treatment. Irreversible sarcoidosis (Stages III and IV), characterized by pulmonary cysts, diffuse parenchymal lung disease, honey comb lung structure (due to consolidation of alveoli) and bronchiectasis, has poor long-term prognosis and a high incidence of pulmonary exacerbations/relapses. Computerized tomography (“CT”) findings for Stages III and IV include bronchiolar nodules (bronchovascular and subpleural), thickened interlobular septae, pulmonary architectural distortion and conglomerate masses. In the approximately 70% of sarcoidosis patients that do not require medical intervention, symptomatic treatment usually consists of non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or aspirin; however, approximately one third of all patients develop a progressive form of chronic sarcoidosis that requires treatment. The first-line therapy for all such chronic sarcoidosis patients is oral steroids (e.g., prednisone or prednisolone) which have significant adverse side effects (susceptibility to infection, osteoporosis and rib fractures from coughing, diabetes, mental confusion, fluid retention, fatigue, etc.) and are not usable for chronic or long term therapy because of these adverse drug responses. In some patients, corticosteroids slow or reverse the course of the disease, but many patients may become refractory to steroids or do not respond at all. Those patients may experience frequent and severe respiratory infections associated with episodes of excessive coughing to dislodge and expel inspissated secretions and cell debris, including granulomas shed into the bronchial lumen. In corticosteroid non-responders with severe symptoms and no treatment options, other cytotoxic agents such as azathioprine, methotrexate, mycophenolic acid, and leflunomide may be tried. Of these, methotrexate is most widely used and is considered a first-line treatment in neurosarcoidosis, often in conjunction with corticosteroids. In general, the cytotoxic agents do not have benefits that outweigh their increased morbidity from cytotoxicity. The only definitive treatment for end-stage disease is lung transplantation and such patients with pulmonary sarcoidosis represent approximately 30% of all lung transplants conducted in the New York Presbyterian, Thoracic Surgery Lung Transplant Service (J.R. Sonnet, personal communication).
Some success in treating sarcoidosis with immunosuppressants has been observed. The rationale for such treatment is that the granulomas involved in sarcoidosis are caused by collections of immune system cells, particularly airway neutrophils and circulating T-cells. Infliximab, a monoclonal antibody that antagonizes the action of TNF-α, has been used to treat pulmonary sarcoidosis in clinical trials, with some success. Etanercept (another TNF-α antagonist), on the other hand, failed to demonstrate any significant efficacy in people with uveal sarcoidosis. The anti-TNF-α monoclonal antibody golimumab also failed to show any benefit in persons with pulmonary sarcoidosis. Adalimumab (yet another anti-TNF-α monoclonal antibody) induced a beneficial response in about half of sarcoidosis patients. See Baughman, et al., 2013, European Respiratory Journal 41:1424-1438.
Individualized therapy is a new paradigm in modern medicine as it transitions from “blockbuster” drugs to stratified personalized medicine. Unfortunately, this approach is not optimally supported by average results from large randomized clinical trials (RCTs). The n=1 approach confers extremely powerful assessment tools to achieve personalized medicine and, using this approach, the patient is the sole unit of observation in therapeutic assessment. The advantages accrued are several. First, in a single patient study, heterogeneity in design is tolerated as long as the single patient stratification arm results in objective evidence favoring the intervention, whereas large population-based RCTs require design uniformity to prevent confounding generalizations. Second, patients in an n=1 trial draw immediate benefit from the trial based on the optimal presentation and refinement of intervention strategies designed to benefit them objectively. This is totally dissimilar to a population-based RCT wherein an individual patient in physical distress may have received a placebo for the entire study period.
Surprisingly, the more powerful n=1 approach has only been used sparingly in general clinical and medical settings, even though it is born out of a recognition that medical interventions that work for a majority of chronic disease conditions have too often proven fruitless in RCTs (Jorgensen, 2008, Expert Rev. Mol. Diagn. 8(6):689-695; Jorgensen, 2009, Oncologist 14(5):557-558). There is a growing presumption that the clinical practice of medicine should recognize and embrace the unique individual characteristics of patients with rare diseases, often needing very costly treatment options, and strive to individualize patient care (Hu et al., 2005, Biotechniques 39(10 Suppl):S1-S6; Langreth & Waldholz, 1999, Oncologist 4(5):426-427; Trusheim et al., 2007, Nat. Rev. Drug Discov. 6(4):287-293).
In the present era of new drug development, large sample parallel group RCT's are often begun without detailed knowledge of the optimal therapeutic dose, patient selection criteria, and initial estimates of the proportion of patients that are responders (important for sample size determination), optimal outcomes on which subsequent trials should be based, safety for long-term/lifetime treatment, etc. In addressing many of these issues in the current environment, where detailed, individualized information is available for single patients, the US National Institutes of Health (NIH) has both advocated and acknowledged the utility of n=1 studies of patient responses to highly individualized therapy in forward-looking “precision medicine” evidence-based approaches. Individualized therapy improves outcome assessment because the treatment regimen is tailored to the patient's disease stratification. For example, the anticancer drug cetuximab (colorectal cancer) is ineffective if the KRAS protein in the tumor has a specific mutation (Van Cutsem et al., 2009, N. Engl. J. Med. 360(14):1408-1417) and the US FDA has relabeled the drug to require genetic profiling before use. Many other drugs have variations in effectiveness in certain patient strata that led to FDA relabeling (e.g., warfarin, carbamazepine, clopidogrel) (Flockhart et al., 2009, Clin. Pharmacol. Ther. 86(1):109-113; Topol, 2010, Sci. Transl. Med. 2(44):44 cm22). Furthermore, the FDA is actively developing streamlined review approaches to companion diagnostic tests with treatments where n=1 protocols facilitate the approval process (Hamburg & Collins, 2010, N. Engl. J. Med. 363(4):301-304).
The n=1 clinical trial approach is very cost effective, but requires much more time commitment and supervision by medical professionals, coupled with suitably long observation intervals, coincident in the index patient with the normal time course of disease progression (interspersed with periodic “cessation of treatment” intervals (or “washout periods”), to test for spontaneous remission of disease). Not only is this targeted n=1 long-term study approach cost effective, but it has also resolved many confounding ambiguities of treatment that would be present in a population study, e.g., diet and lifestyle changes, progression/regression of disease, meaningful patient benefit, etc. The n=1 approach reflects the trend toward “personalized medicine” of the future and has a high degree of quasi-statistical precision because the patient serves as his or her own control, increasing confidence in the results of customized treatment. In fact, n=1 clinical studies could be deemed virtually essential for evaluation of highly targeted therapies, many of which may not even be amenable to RCTs because the between variance for treatments would be large relative to the relatively small sample size for an extremely rare disease. In such cases, the n=1 approach epitomizes the appropriateness of clinical trial designs which minimize the time a patient is given a suboptimal intervention. Moreover, sequential designs with lengthy data collection processes are especially useful for rare, unique diseases (Everitt & Pickler, 2004, Statistical Aspects of The Design of Clinical Trials. Imperial College Press; London, UK; Gerss & Kopcke, 2010, Adv. Exp. Med. Biol. 686:173-190; Meinert & Tonascia, 1986, Clinical Trials Design, Conduct, and Analysis Monographs in Epidemiology and Biostatistics. Vol. 469. Oxford University Press; NY, USA).
The ultimate clinically important issue for novel interventions with utility is generalizability of results to subpopulations. It is here that n=1 clinical trials excel, enabling stratification of patients into groups more or less likely to benefit from a specific treatment for population-level association studies (Barlow et al., Strategies for Studying Behavior for Change. 3. Vol. 393. Pearson/Allyn and Bacon; MA, USA; Guyatt et al., 1986, N. Engl. J. Med. 314(14):889-892). Individual variations in response to treatment reflect population variations and if stratifications are well described (Kraemer et al., 2002, Arch. Gen. Psychiatry 59(10):877-883; Kent & Hayward, 2007, JAMA 298(10):1209-1212; Scuffham et al., 2010, J. Gen. Intern. Med. 25(9):906-913), n=1 clinical trials objectively quantify this variability and provide informed guidance for treating individual patients using their own data. The efficiency of n=1 clinical trials in identifying and minimizing suboptimal treatments is far greater than standard care utilizing RCTs, both improving patient management and resulting in cost savings.